Fix configuration for plugin and extension API artifact deployment

Add the necessary settings in the fake pom.xml file, and correct the URL
in the BUCK file to make deployment with gs-maven-wagon work.

Change-Id: I6d1f84c850c70f731d061d9e50a062d37c68baf2
Buck: add build for gerrit-plugin-gwtui

This plugin module was left out during Buck migration.

  $>buck build api

produces now plugin-gwtui.jar and plugin-gwtui-src.jar.

Buck Maven bridge was enhanced to {install|deploy} the new artifact to
remote or local Maven repositories:

  $>buck build install_api

deployes

  gerrit-plugin-gwtui-2.9-SNAPSHOT-sources.jar
  gerrit-plugin-gwtui-2.9-SNAPSHOT.jar

to local Maven repository.

Change-Id: Idae18f6df2e67fe53d57b8c35caa4226333e269b
(cherry picked from commit c8cffc8e928a9277621ffff6cb740f79cd662195)
Merge branch 'stable-2.8'

* stable-2.8:
  Buck: add build for gerrit-plugin-gwtui
  Fix configuration for plugin and extension API artifact deployment

Conflicts:
	BUCK
	gerrit-plugin-gwtui/BUCK
	tools/maven/BUCK

Change-Id: I4267b0a6397823a00a11db268b02a50c4f79d4ed
Merge "Merge branch 'stable-2.8'"